The present invention relates to a plasma processing method and apparatus to be used for manufacture of semiconductor or other electron devices and micromachines.
In the manufacture of semiconductor or other electron devices and micromachines, thin-film processing techniques using plasma processing have been becoming increasingly important in recent years.
As an example of conventional plasma processing methods, plasma processing using a patch-antenna type plasma source is described below with reference to FIG. 5. Referring to FIG. 5, while interior of a vacuum chamber 1 is maintained to a specified pressure by introducing a specified gas from a gas supply unit 2 into the vacuum chamber 1 and simultaneously performing exhaustion by a turbo-molecular pump 3 as an exhauster, a high-frequency power of 100 MHz is supplied by an antenna use high-frequency power supply 4 to an antenna 5 provided so as to project into the vacuum chamber 1. Then, plasma is generated in the vacuum chamber 1, allowing plasma processing to be carried out with a substrate 7 placed on a substrate electrode 6. There is also provided a substrate-electrode use high-frequency power supply 8 for supplying high-frequency power to the substrate electrode 6, making it possible to control ion energy that reaches the substrate 7. The high-frequency voltage supplied to the antenna 5 is delivered to a proximity to the center of the antenna 5 by a feed bar 9. A plurality of sites of the antenna 5 other than its center and peripheries, and a face 27 of the vacuum chamber 1 opposite to the substrate 7 are short-circuited by short pins 10. A dielectric plate 11 is sandwiched between the antenna 5 and the vacuum chamber 1, and the feed bar 9 and the short pins 10 serve to connect the antenna 5 and the antenna use high-frequency power supply 4 to each other, and the antenna 5 and the vacuum chamber 1 to each other via through holes provided in the dielectric plate 11. Also, surfaces of the antenna 5 are covered with an antenna cover 15. The antenna cover 15 is fixed to the antenna 5 by bolts 25. Further, a slit 14 is provided so as to comprise a recessed or grooved space between the dielectric plate 11 and a dielectric ring 12 provided at a peripheral portion of the dielectric plate 11, and a recessed or grooved space between the antenna 5 and a conductor ring 13 provided at a peripheral portion of the antenna 5.
The turbo-molecular pump 3 and an exhaust port 19 are disposed just under the substrate electrode 6, and a pressure-regulating valve 20 for controlling the vacuum chamber 1 to a specified pressure is an up-and-down valve disposed just under the substrate electrode 6 and just over the turbo-molecular pump 3. The substrate electrode 6 is fixed to the vacuum chamber 1 with four pillars 21.
In the plasma processing described in the above prior-art example, however, plasma density would become the highest at the slit, posing an issue of damage of a bottom face 26 of the slit. The vacuum chamber, which is typically made of aluminium, is generally coated with anodic oxide (alumite) for prevention of corrosion of the inner wall surface of the vacuum chamber. However, the alumite of the slit bottom face would be damaged and, over repeated plasma processing, the alumite would become gradually thinner and thinner. According to our experiments, when the thickness of alumite was measured before and after an about 1,000 pcs. etching process, an about 10 xcexcm decrease of film thickness was found. Shortage of the alumite thickness would lead to problems such as corrosion of base-material aluminium or occurrence of dust. For prevention of this, it is necessary to disassemble most of the plasma source unit and replace the aluminium member, which is heavy and expensive, unfortunately. Furthermore, since the antenna cover 15 is fixed to the antenna 5 by the bolts 25, deposited film resulting from the plasma processing tends to be peeled off from the vicinities of the bolts 25, causing occurrence of dust, as another problem.
Meanwhile, in the plasma processing described in the prior-art example, there is an issue that the temperature of the antenna cover 15 increases due to plasma exposure. Since the antenna cover 15 and the antenna 5 are vacuum-insulated from each other, the temperature of the antenna cover 15 gradually increases over repeated plasma processing. According to our experiments, it was found that the temperature of the antenna cover 15 increases up to 170xc2x0 C. after 5-min. plasma processing and 1-min. vacuum holding is repeated six times. Such an abrupt change in the temperature of the antenna cover 15 may cause not only occurrence of dust but also cracks of the antenna cover 15.
In view of these and other prior-art issues, an object of the present invention is to provide a plasma processing method and apparatus which is less liable to occurrence of dust and cracks of the antenna cover.
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a plasma processing method for generating plasma in a vacuum chamber and processing a substrate placed on a substrate electrode, the plasma being generated by supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna provided opposite to the substrate electrode while interior of the vacuum chamber is controlled to a specified pressure by supplying a gas into the vacuum chamber and exhausting the interior of the vacuum chamber,
the method comprising: with a dielectric plate being sandwiched between the antenna and the vacuum chamber and both the antenna and the dielectric plate projecting into the vacuum chamber,
controlling plasma distribution on the substrate with an annular and recessed slit provided between the antenna and the vacuum chamber; and
processing the substrate in a state where the antenna cover is fixed by making both an inner side face of the slit and the antenna covered with an antenna cover, making a bottom face of the slit covered with a slit cover, supporting the antenna cover by the slit cover, and fixing the slit cover to a wall surface of the vacuum chamber.
According to a second aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed with the slit cover is a conductor and with electric conduction between the slit cover and the vacuum-chamber wall surface ensured by a spiral tube.
According to a third aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed with the slit cover is an insulating member.
According to a fourth aspect of the present invention, there is provided a plasma processing method for generating plasma in a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the plasma being generated by supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna provided opposite to the substrate electrode while interior of the vacuum chamber is controlled to a specified pressure by supplying a gas into the vacuum chamber and exhausting the interior of the vacuum chamber,
the method comprising: with a dielectric plate being sandwiched between the antenna and the vacuum chamber and both the antenna and the dielectric plate projecting into the vacuum chamber,
controlling plasma distribution on the substrate by an annular and recessed slit provided between the antenna and the vacuum chamber; and
processing the substrate while controlling temperature of the antenna by making both an inner side face of the slit and the antenna covered with an antenna cover and applying a refrigerant flow to the antenna while ensuring heat conduction between the antenna and the antenna cover by a heat-conducting sheet provided between the antenna and the antenna cover.
According to a fifth aspect of the present invention, there is provided a plasma processing method according to the fourth aspect, wherein the substrate is processed while the temperature of the antenna is controlled with the heat-conducting sheet being made from a resin having elasticity and having a dielectric loss tangent of more than 0 and not more than 0.01.
According to a sixth aspect of the present invention, there is provided a plasma processing method according to the fourth aspect, wherein the substrate is processed while the temperature of the antenna is controlled with the heat-conducting sheet having a thickness of 0.03 mm to 3 mm.
According to a seventh aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the antenna cover is made of 1 mm to 10 mm thick quartz glass.
According to an eighth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed with the antenna cover being made of 1 mm to 10 mm thick insulative silicon.
According to a ninth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed with the frequency of the high-frequency power supplied to the antenna being within a range of 50 MHz to 300 MHz.
According to a 10th aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber;
a gas supply unit for supplying gas into the vacuum chamber;
an exhausting unit for exhausting interior of the vacuum chamber;
a pressure-regulating valve for controlling the interior of the vacuum chamber to a specified pressure;
a substrate electrode for placing thereon a substrate within the vacuum chamber;
an antenna provided opposite to the substrate electrode; and
high-frequency power supply capable of supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to the antenna,
the plasma processing apparatus further comprising:
a dielectric plate sandwiched between the antenna and the vacuum chamber, both the antenna and the dielectric plate projecting into the vacuum chamber;
an antenna cover for covering both an inner side face of an annular and recessed slit and the antenna with the slit provided between the antenna and the vacuum chamber; and
a slit cover for covering a bottom face of the slit and supporting the antenna cover, where the slit cover is fixed to a wall surface of the vacuum chamber so that the antenna cover is fixed.
According to an 11th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the slit cover is a conductor and electric conduction between the slit cover and the vacuum-chamber wall surface is ensured by a spiral tube.
According to a 12th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the slit cover is a dielectric substance.
According to a 13th aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber;
a gas supply unit for supplying gas into the vacuum chamber;
an exhausting unit for exhausting interior of the vacuum chamber;
a pressure-regulating valve for controlling the interior of the vacuum chamber to a specified pressure;
a substrate electrode for placing thereon a substrate within the vacuum chamber;
an antenna provided opposite to the substrate electrode; and
high-frequency power supply capable of supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to the antenna,
the plasma processing apparatus further comprising:
a dielectric plate sandwiched between the antenna and the vacuum chamber, both the antenna and the dielectric plate projecting into the vacuum chamber;
an antenna cover for covering both an inner side face of an annular and recessed slit and the antenna with the slit provided between the antenna and the vacuum chamber;
a heat-conducting sheet provided between the antenna and the antenna cover; and
a refrigerant feed unit for making a refrigerant flow to the antenna.
According to a 14th aspect of the present invention, there is provided a plasma processing apparatus according to the 13th aspect, wherein the heat-conducting sheet is made from a resin having elasticity and having a dielectric loss tangent of more than 0 and not more than 0.01.
According to a 15th aspect of the present invention, there is provided a plasma processing apparatus according to the 13th aspect, wherein the heat-conducting sheet has a thickness of 0.03 mm to 3 mm.
According to a 16th aspect of the present invention, there is provided a plasma processing apparatus according to the tenth aspect, wherein the antenna cover is made of 1 mm to 10 mm thick quartz glass.
According to a 17th aspect of the present invention, there is provided a plasma processing apparatus according to the tenth aspect, wherein the antenna cover is made of 1 mm to 10 mm thick insulative silicon.
According to an 18th aspect of the present invention, there is provided a plasma processing apparatus according to the tenth aspect, wherein the frequency of the high-frequency power supplied to the antenna is within a range of 50 MHz to 300 MHz.